PROJECT SUMMARY Morphea is a disfiguring autoimmune disease of the skin and underlying tissue. An unbalanced inflammatory response leads to fibrosis and atrophy of the deeper tissue, causing physical and psychological disability. Available therapies for morphea are not always efficacious and are often associated with substantial side effects. One of the biggest barriers to the development of new treatments is a lack of studies examining the pathophysiology of morphea, the initial step that leads toward the development of more directed and efficacious therapies. The Morphea in Adults and Children (MAC) and National Registry for Childhood Onset Scleroderma (NRCOS) registries, led by the principal investigators (Jacobe and Torok, respectively), have already begun to address this problem. Working together, we have investigated the protein expression and bulk transcriptional profile associated with morphea in both children and adults using protein assay, cytometry, and microarray/RNA sequencing. These data indicate that fibrosis in morphea is driven by inflammation through a network of IFN? mediated genes. Despite this progress, the pathogenesis of morphea, including the exact cell populations? producing this IFN? over expression, needs to be examined in depth before new treatments can be tested. That is the goal of this proposal. Our studies leverage the unique resources of the MAC and NRCOS registries (the largest in the world) and the multidisciplinary and complementary expertise of the investigators (including facilities at UTSW Medical Center and the University of Pittsburgh) to conduct detailed transcriptional and mechanistic studies to fully investigate transcriptional profiles of likely pathogenic cell types and study the immunological effects of key molecules in a morphea mouse model. An additional resource includes collaboration with Dr. Jillian Richmond at the University of Massachusetts, who will provide insight and expertise of studying the IFN? chemokine axis in the morphea mouse model. The objectives of the proposed studies are to: 1) further define dysregulated immune pathways in morphea by identifying inflammatory cell subsets that express these IFN? mediated genes, which are likely the pathogenic cell subtypes, 2) determine fibroblast subsets and their interaction with pathogenic inflammatory cells, 3) and define the pathogenic pathways that enable the disease, by first utilizing a mouse model. The conduct of these studies will not only probe morphea to find the underlying disease mechanism, but will also produce promising targets for development of new therapies.